Mutant Glutathione-S-Transferases (GST) were expressed and purified from wild-type yeast, map1 yeast, and map2 yeast. Since methionine aminopeptidases (MetAPs) are involved in N-terminal processing, we predict that GSTs expressed in yeast strains lacking either MetAP1 or MetAP2 should not have their N-terminal methionine completely removed. We hope using mass spectrometry to analyze the extent of met-removal of different GSTs to understand the roles of two distinct MetAPs. We are using a series of mutant glutathionine-S-transferases to evaluate the roles of each methionine aminopeptidases in eukaryotic cells.